I. Field of the Invention
This invention relates generally to rotary, kinetic fluid motors of the type seen generally in United States Class 415, Subclasses 90-92. More particularly, the invention relates to pneumatic, turbine vibrators of the type classified in United States Patent Class 366 (i.e., "Agitators"), Subclasses 124 and 125.
II. Description of the Prior Art
A number of rotary, kinetic motors and vibrators have evolved over the years. Broadly speaking, such devices typically comprise a rigid housing that encloses a rotary turbine wheel. The wheel may be mounted to a suitable shaft supported by bearings on opposite sides of a receptive chamber. Air inlet and exhaust ports in fluid flow communication with the chamber establish a high-pressure air pathway through the housing that activates the rotor. The wheel comprises radially formed buckets, vanes, or blade elements at its periphery that are interposed within the airflow to produce rotation. When deployed as a motor, such devices include a working shaft splined to a balanced turbine wheel that outputs useful work. Powerful pneumatic turbine vibrators result by unbalancing the turbine wheel.
It has long been recognized by those skilled in the art that turbine vibrators offer many advantages over other types of popular vibrators. For example, properly designed turbine vibrators are smaller and more compact than similarly powered mechanical units comprising unbalanced balls, weights or shafts. By avoiding the vibrating balls or weights that are used in prior designs, substantial wear can be reduced, and reliability thus increases. Pneumatic vibrators are easier to power in many industrial environments because HP air is widely available. Ball vibrators tend to be loud and inefficient. Thus a number of turbine vibrators have been proposed in the art and many designs are in widespread use. However, many prior art turbine vibrators exhibit relatively high noise levels that often exceed 100 decibels. The power of the spectral noise outputted by many older turbine vibrators is often concentrated in higher frequency regions of the audio spectrum that are particularly dangerous to human hearing. In most cases it is no longer appropriate to install old fashioned turbine vibrators because they exceed the tolerance level of 85 decibels for continuous operation established by the OSHA Act of 1970.
U.S. Pat. No. 2,793,009 discloses a pneumatic ball vibrator having a casing defining an internal, rotary chamber. The generally cubical casing includes suitable tabs for mounting the unit in a desired location. Air inlets and outlets in fluid flow with the chamber interior establish a vigorous airflow. Vibration results as the ball forcibly impacts the rigid race within the interior.
U.S. Pat. No. 3,672,639 discloses a rigid vibrator having a case that mounts a rotary cylinder and vane arrangement. Vibration is pneumatically obtained from the resultant mechanical impact of rotating sleeves. However, both this design and older ball vibrator systems are no longer favored, as substantial benefits involving noise reduction, production cost and overall efficiency result from the use of rotary turbine vibrators such as those discussed below.
Pneumatic vibrators disclosed in U.S. Pat. Nos. 1,346,221, 2,875,988 and 2,960,316 employ rotary turbine wheels confined within rigid casings. Each turbine wheel has a circular periphery comprising a plurality of radially spaced-apart "saw teeth" interposed within an air path established though the casing. In each of these turbine vibrators air escapes from the turbine wheel teeth almost immediately after rotation begins. None of these designs provides a means whereby pressurized air traveling through the apparatus is redirected downstream through adjacent vents in the turbine housing. Instead, these older designs apply working air pressure only to a limited number of teeth. Pressure is radically dissipated as these designs lack appropriate seals between the rotor teeth and adjacent casing surfaces. In the latter two designs air pressure is vented to atmosphere through passageways adjacent the turbine wheel ends. High-pressure air is not redirected to the turbine wheel periphery to extract additional work before venting.
U.S. Pat. Nos. 3,932,057, 3,939,905, and 3,870,282 relate to high speed, low noise pneumatic vibrators. Special turbine wheel teeth and vent systems are employed to minimize noise. However, these designs are not aimed at vent redirection or power gain. Other prior art designs pertinent to the instant disclosure are seen in prior U.S. Pat. Nos. 3,074,151, 3,304,051, 3,945,757, 4,232,991, and 5,314,305.
U.S. Pat. No. 4,604,029 discloses a rotary pneumatic vibrator in which the air path is modified. A special two-section rotary impeller is mounted for rotation with a cylindrical chamber, whose periphery has small, spaced-apart pockets machined into it. These pockets modify the airflow established between the chamber inlet and outlets, purportedly increasing the radially turning forces exerted on the rotor while at the same time quieting the device.
The worth of "return stages" in the periphery of turbine rotor housings has been recognized in a paper by Silvern and Balje entitled "A Study of High Energy Level, Low Output Turbines," AMF/TD No. 1196, Department of the Navy, Office of Naval Research, Contract No. NONR-2292(00) published Apr. 9, 1958. This study suggests that the efficiency of Terry turbine rotors may be increased with certain modifications to the rotor housing periphery. Reentry ports or return stages defined in the air path can increase the resultant force of the rotor, without detracting from the other known benefits that Terry wheel turbine motors can provide.